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Study of structural and optical properties of TiO2:Tb thin films prepared by high energy reactive magnetron sputtering method

Domaradzki J., Kaczmarek D., Prociow E. L., Wojcieszak D., Sieradzka K., Mazur M., Lapinski M.

Optica Applicata

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2009

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Vol. 39, nr 4

815-823

EN

This work is focused on structural and optical properties of TiO2 thin films doped with different amount of terbium. The thin films have been prepared by high energy reactive magnetron sputtering (HE RMS) and by low pressure hot target reactive magnetron sputtering (LP HTRS) processes. Thin films were deposited from mosaic, metallic Ti-Tb target sputtered under oxygen plasma (without argon) at a pressure below 10-1 Pa. Structural examinations show nanocrystalline nature of prepared thin films with either anatase or rutile phases depending on concentration of Tb 0.4 at.% and 2.6 at.%, respectively. The phase transformation from the anatase to the rutile has not been observed after additional post-deposition annealing even at the temperature up to 1000 K. Based on investigations performed with the help of atomic force microscope high nanocrystalline, close-packed structure has been found. Studies of refraction index revealed higher value for the thin films prepared by the HE RMS than by the LP HTRS methods.

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Study of structural and optical properties of TiO2:(Eu, Pd) thin films deposited by magnetron sputtering

Kaczmarek D., Domaradzki J., Prociow E. L., Wojcieszak D., Michalec B.

Materiały Elektroniczne

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2008

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T. 36, nr 3

117-127

EN

In this study the results on TiO2 thin films doped with europium and palladium at the amount of 0.9 at. % and 5.8 at. % respectively have been presented. For thin films deposition the high energy (HE) magnetron sputtering method was used. Some samples were subjected to the post-processed annealing. X-Ray Diffraction (XRD) results have shown that after deposition nanocrystalline TiO2 - rutile structure was obtained. After additional annealing at 800°C average crystallites sizes increased about twofold (from 9 to 16 nm). The XRD results were confirmed using atomic force microscope. Optical properties of thin films were examined using optical transmission method. They have shown that doping with Eu and Pd has decreased the transmission level by about 15% and shifted absorption edge to the longer wavelength range (from 330 to 450 nm) compared to pure TiO2. The width of optical bandgap of TiO2:(Eu, Pd) thin film decreased to ca. 1.7 eV, i.e. twofold, when compared to 3.35 eV of undoped-TiO2. The photoluminescence results have shown that examined thin film has strong red luminescence from standard Eu3+ emission lines.

PL

W pracy przedstawiono wyniki badań cienkich warstw TiO2 domieszkowanych europem i palladem, w ilości odpowiednio 0,9 % at. i 5,8 % at. Do nanoszenia cienkich warstw zastosowano wysokoenergetyczny proces (High Energy) rozpylania magnetronowego. Wybrane próbki poddano dodatkowemu poprocesowemu wygrzewaniu. Wyniki dyfrakcji rentgenowskiej (X-Ray Difrraction - XRD) wykazały, że bezpośrednio po naniesieniu otrzymano nanokrystaliczną warstwę TiO2 o strukturze rutylu. Po dodatkowym wygrzewaniu w temperaturze 800°C średnia wielkość krystalitów wzrosła około dwukrotnie (z 9 do 16 nm). Wyniki badań XRD zostały potwierdzone za pomocą badań wykonanych za pomocą mikroskopu sił atomowych. Właściwości optyczne cienkich warstw określono na podstawie wyników badań metodą transmisji światła. Uzyskane wyniki wykazały, że domieszkowanie Eu i Pd spowodowało spadek przezroczystości warstwy o ~ 15% i przesunięcie krawędzi absorpcji optycznej w stronę dłuższych fal (z 330 do 450 nm) w porównaniu do warstwy niedomieszkowanego TiO2. Szerokość optycznej przerwy zabronionej dla cienkiej warstwy TiO2:(Eu, Pd) po naniesieniu wynosiła 1,7 eV i była około dwukrotnie mniejsza w porównaniu do 3,35 eV dla warstwy TiO2. Wyniki badań foto-luminescencji pokazały, że badana warstwa wykazuje silną czerwoną luminescencję odpowiadającą standardowym linią emisyjnym Eu3+.

3

Evaluation of electrical properties of Eu and Pd-doped titanium dioxide thin films deposited on silicon

Prociow E. L., Domaradzki J., Kaczmarek D., Sieradzka K., Michalec B.

Materiały Elektroniczne

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2008

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T. 36, nr 4

149-156

EN

In this work, investigations of electrical properties of Eu and Pd-doped TiO2 thin films have been outlined. Our previous studies [4, 6] of Eu and Pd-doped TiO2, have shown the nanocrystalline structure and high transparency in visible region (about 70%). Now, it has been shown that by incorporation of Pd and Eu dopants into TiO2 matrix, its properties can be modified so as to obtain simultaneously electrically and optically active oxide-semiconductor with specified type of electrical conduction at room temperature. Pd dopant changes the electrical properties of TiO2 from dielectric oxide to conducting oxide. Samples were examined by means of theromelectrical, current-voltage (I-V), transient photovoltage and optical beam induced current OBIC (Optical Beam Induced Current). I-V measurements showed formation of electrical junctions at the interface of semiconducting thin films of metal oxides and silicon substrate (TOS-Si). The presence of build-in potential has been confirmed by OBIC through created maps of photocurrent distribution generated in the active areas of prepared TOS-Si heterojunctions.

PL

W niniejszej pracy przedstawiono badanie właściwości elektrycznych cienkich warstw TiO2 domieszkowanych Eu i Pd. Pokazano, że wprowadzenie domieszki Eu i Pd do matrycy TiO2 modyfikuje jej właściwości, pozwala otrzymać cienkie warstwy elektrycznie i optycznie aktywne. Dodatkowo, wytworzone tlenki posiadają określony typ przewodnictwa elektrycznego w temperaturze pokojowej. Decydujący wpływ na właściwości elektryczne matrycy TiO2 miała domieszka Pd, która umożliwiła zmianę właściwości cienkich warstw dielektrycznych na półprzewodnikowe. Próbki badano za pomocą charakterystyk termoelektrycznych, charakterystyk prądowo-napięciowych (I-V) oraz metodą OBIC. Na podstawie pomiarów I-V zaobserwowano formowanie się złącza na granicy przezroczysty tlenek półprzewodnikowy-podłoże krzemowe (TOS-Si). Mapy rozkładu fotoprądu generowanego w obszarach aktywnych wytworzonego heterozłącza TOS-Si potwierdziły obecność potencjału wbudowanego.

4

Optical and electrical properties of TiO2 doped with Tb and Pd

Domaradzki J., Kaczmarek D., Prociow E. L., Borkowska A., Berlicki T., Sieradzka K.

Materials Science Poland

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2008

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Vol. 26, No. 1

143--147

EN

Optical and electrical properties of TiO2 doped with 0.6 at. % Tb and 9 at. % Pd have been investigated. Thin films were deposited by low pressure hot target reactive sputtering from a metallic Ti-Tb-Pd mosaic target on silicon and glass substrates. Total concentration of Tb and Pd was determined using an energy disperse spectrometer. Optical properties were studied by means of optical transmission. It has been shown that Tb dopant does not make any significant changes in the transmission level. Pd dopant shifts the fundamental absorption edge of TiO2 towards longer wavelengths and decreases the transmission to about 40%. For electrical characterization of the prepared thin films, temperature dependent resistivity and current-voltage (I-V) characteristics have been examined. It has been shown that incorporation of Pd and Tb into TiO2 matrix modifies its properties allowing one to obtain p-type oxide-semiconductor electrically and optically active at room temperature. Additionally, based on I-V measurements, the formation of heterojunction at the interface of thin film-silicon was confirmed.

5

Influence of substrate type and its placement on structural properties of TiO2 thin films prepared by the high energy reactive magnetron sputtering method

Kaczmarek D., Prociow E. L., Domaradzki J., Borkowska A., Mielcarek W., Wojcieszak D.

Materials Science Poland

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2008

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Vol. 26, No. 1

113--117

EN

The paper presents studies of the influence of substrate type and its placement on structural properties of TiO2 thin films prepared by the high energy reactive magnetron sputtering method. During the deposition, conditions of the magnetron powering have been especially selected to enhance the nucleation energy. Thin films were deposited on Si(100) and SiO2. Substrates were placed on a plate at three distances from the centre of the target. Selected substrates were also placed under various angles with respect to the plate. Thin films were examined using X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD analysis showed existence of TiO2-rutile phase with preferred (110) orientation and AFM measurements revealed nanocrystalline structure of the films.

6

Investigations of electrical properties of Eu- and Pd-doped titanium dioxide thin films on silicon

Domaradzki J., Borkowska A., Kaczmarek D., Prociow E. L.

Optica Applicata

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2007

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Vol. 37, nr 1-2

133-137

EN

In this work, investigations of electrical properties of Eu- and Pd-doped TiO2 thin films have been outlined. Thin films were deposited by low pressure hot target reactive magnetron sputtering from metallic Ti-Eu-Pd mosaic target on conventional silicon wafers. For electrical characterization of prepared thin films both temperature dependent resistivity and current to voltage (I-V) characteristics have been examined. It has been shown that incorporation of Pd and Eu dopants into TiO2 matrix modified its properties to obtain n-type oxide-semiconductor which is electrically and optically active at room temperature. Additionally from I-V measurements the formation of heterojunction at the interface of thin film-silicon was confirmed.